For custom crush / contract winemaking you may like to report on all the bulk wines including their compositions for your customers.
The best report for this is the Bulk Stock Report available under Winery Reports> Bulk Wine> Bulk Stock Report.
To see the composition you need to ensure Composition details is checked. Then you can select from a variety of different grouping options. The most common are Grouped Origin or a straight Origin breakdown. You may need to play around with these options to find what works best for you.
There is also the option to report this information in CSV (Excel) by changing the format to CSV instead of PDF. With CSV selected you can also check the option called Breakdown Comp. This option will add a unique line in the spreadsheet for each composition element which can be more intuitive to read, particularly if the composition information is important to you. i.e. A 50/50 blend of 2008 Yarra Valley Chardonnay and 2009 Yarra Valley Marsanne will have two lines within the resulting CSV, each with a 50% composition factor.
Again, play around with this option as the composition grouping you have selected will also impact the output.
You can of course use any number of the other filters available for this report including the Owner which can be set to a particular custom if you process any custom crush / contract wine.